The present invention relates generally to a wound care dressing and more specifically relates to a wound care sponge constructed of a polyvinyl acetal composition with an outer low durometer silicone skin ranging from 1-4 mils in thickness.
There are a number of major problems encountered in present day wound dressings. Such wound dressings are primarily of the cellulose type and the sponge type. Cellulose dressings have probably have been used in some form since the beginning of recorded history and are basically constructed of cellulose materials such as rayon and cotton. These wound dressings leave Tinting fibers, allow bacterial growth adjacent the wound and allow wound growth extension into the fibers of the dressing. Removal of the dressing also causes tearing of the wound when the dressing is removed and can leave fibrous fragments in the wound. Because of the fiber spacing in such dressings they also do not present a barrier against direct exposure to air and organisms carried in the air.
Advances in the development of synthetic polymers have produced numerous changes in wound care dressings resulting in polymeric foams, polymeric foams, particulate and fibrous polymers, hydrogels and hydrocolloids. These developments have resulted in sponge type dressings being widely used but unfortunately these dressings also suffer from wound growth into the cells of the sponges, lack of absorption and wound tearing problems which occur when the dressings are removed.
A number of sponge type dressings and medical devices have been constructed of PVA material. These products have a significant percent of their alcohol functions acetalized and are open celled, highly water absorbent porous flexible material that wick aqueous solutions quickly. They have high tensile strength, good elongation and excellent resistance to most chemicals and are white in color.
U.S. Pat. No. 4,098,728 issued Jul. 4, 1978 discloses the use of polyvinyl acetal material having a fast wicking and high liquid holding capacity for medical usage.
U.S. Pat. No. 5,071,648, issued on Dec. 10, 1991 discloses a polyvinyl acetal material with a complex of iodine which forms a sponge releasing controlled amounts of iodine sufficient to kill germ cells with minimum toxicity to the surrounding tissue. Likewise, U.S. Pat. No. 5,744,150 issued on Apr. 28, 1998 and U.S. Pat. No. 5,928,665 issued Jul. 27, 1999 disclose a method for producing an antimicrobial iodine polyvinyl acetal sponge which is soaked in a aqueous bath of 20% to 70% triethylene glycol. The resultant product is a wound dressing including an iodine complexed polyvinyl acetal sponge material in which alkylene glycol is applied to the surface of the sponge to soften the sponge and impart a yellow-gold coloration onto the outer surface of the sponge indicating the activation of the antimicrobial elements complexed in the sponge material. U.S. Pat. No. 5,810,755 issued Sep. 22, 1998 discloses a medicated wound dressing with a open cell foam polymeric compound of polyvinyl alcohol complexed with elemental iodine.
U.S. Pat. No. 5,554,659 issued Sep. 10, 1996 and U.S. Pat. No. 5,556,391 issued Sep. 17, 1996 are directed toward a molded porous polyvinyl alcohol sponge including an outer skin having an average pore size smaller than the interior portion of the product capable of absorbing and passing water to the interior portions of the sponge.
U.S. Pat. No. 5,811,471, issued Sep. 22, 1998 discloses a polyvinyl acetal polymer sponge which has a germicidal disinfectant dye bound thereto which is used as a tampon while U.S. Pat. No. 5,447,505 issued Sep. 5, 1995 discloses the use of polyvinyl acetal sponge a surgical dressing. Polyvinyl acetal is already used in the prior art for nasal packings and other surgical packings.
Another article in the prior art as shown in U.S. Pat. No. 5,466,231 issued Nov. 14, 1995 adheres or laminates a layer or sheet of polyethylene to the large lateral surfaces of a polyvinyl acetal sponge and then perforates the polyethylene sheet to allow moisture transfer. The product works but the polyethylene skin cannot be compressed because it will delaminate. As a result, the product in the single compressed dimension is too large to permit comfortable insertion.
U.S. Pat. No. 5,370,656 inferentially discloses proving a fluid impervious silicone layer to a polyvinyl acetal xe2x80x9cCxe2x80x9d shaped throat pack sponge.
Materials that are closely related chemically to the polyvinyl acetate-alcohol-acetal porous bodies of this invention have been used in a variety of biologically related applications. The following uses of related materials is considered exemplary and illustrative of such uses. Tan, J. H.,; et al, (Radiation Research, vol. 124, no. 1, p. 43-9, October 1990) implanted a polyvinyl alcohol sponge disc in the subcutis of the thorax. A separating agent which includes a polyvinyl acetal resin having open cell structure and an average pore size of from about 10 to about 1000 micrometers has been described in U.S. Pat. No. 5,085,781 issued Feb. 4, 1992. U.S. Pat. No. 5,370,656 issued Dec. 6, 1994 describes a throat sponge which maybe pre-hydrated which is made from polyvinyl acetal that is fast working and expands instantly and uniformly to absorb 23 to 27 times its weight in fluids.
The present invention solves the above noted problems with wound care sponges in a manner not disclosed in the known prior art.
The present invention is directed toward a polyvinyl acetal wound care sponge with a smooth outer silicone skin bonded thereto, the skin having less porosity then the foam center and a low durometer. The PVA sponge is washed free of formaldehyde, dried and hydrated and a thin coating of low durometer silicone is applied to the surface of the sponge and heated at a low temperature over 8 to 16 hours to cure the silicone skin bonding it to the sponge increasing the tear strength of the skin while preserving elasticity. The cured skin has an elongation expansion ranging from about 200 to about 600% and increased tear strength. The composite wound dressing allows moisture adsorption through the silicone skin into the PVA sponge body but presents a smooth outer surface precluding wound growth into the sponge material.
It is an object of the invention to provide a wound care dressing having a slightly porous skin to allow for the passage of moisture into the sponge body.
It is another object of the invention to provide a wound care dressing having a skin of a different material from the body of the dressing which exhibits physical properties similar to the PVA sponge in elasticity and strength.
It is yet another object of the invention to provide a wound care dressing which is soft and flexible while exhibiting better fluid retention with less leakage than prior art wound care sponges.
It is still another object of the invention to provide a wound dressing which allows comfortable easy removal of the dressing from the wound and upon removal leaves the wound area clean with minimal tearing of the wound area.
In the accompanying drawings, there is shown an illustrative embodiment of the invention from which these and other objectives, novel features and advantages will be readily apparent.